1. Field of the Invention
The present invention relates to an exchange, more particularly relates to an exchange of a communications system in which terminal equipment (TE) having its own terminal identifier information is connected to the exchange with a point to point configuration and a logical link is established conditional on a match, by a layer 2 procedure, of the terminal identifier information before link establishment and thereafter call processing, by a layer 3 message, is carried out.
The leading user-network interface of this type of communications system in Japan in the basic rate interface (BRI) of the integrated services digital network (ISDN). In this BRI, accommodation of a plurality of terminal equipment by logical link, portability of of terminal equipment, and so on are guaranteed. Depending on the mode of operation of the network, however, there are cases where the terminal endpoint identifiers (TEI) will not match between the exchange side and terminal equipment to be connected. If this unmatching occurs, the logical link will not be able to be established and users will not be able to communicate. Therefore, solution of this problem has been demanded.
2. Description of the Related Art
As will be explained in detail later by using the drawings, in such a point to point configuration BRI, at the time of reception, mistakes in input of subscriber data (TEI values) or mistakes in the setup of the subscriber data at the terminal equipment TE side sometimes results in the TEI value of the network side and the TEI value of the terminal equipment TE side not matching from the first.
Further, even if the TEI values of the two match at an initial stage, later changes in the terminal equipment TE etc. can cause the TEI value of the terminal equipment TE side to change. If this is not notified to maintenance personnel of the network side of if notified, but the TEI value of the network side is not properly changed, the values may not match.
Further, it is also possible to agree in advance to determine the TEI values of all subscribers as fixed values (for example, TEI=0) and use the fixed TEI values to establish, by the subscriber, the link access procedure on the D-channel (LAPD) call by call or at the input of the subscriber data. However, lack of thorough knowledge of the fixed TEI values or mistakes in the setup of the TEI values of the terminal equipment TE side etc. will cause the values not to match.
An object of the present invention is to provide, in view of the above problem, an exchange not allowing unmatching terminal identifier information between the exchange and subscriber terminal equipment having its own terminal identifier information.
To attain the above object, according to the present invention, there is provided an exchange of a communications system in which terminal equipment having its own terminal identifier information is connected to the exchange with a point to point configuration, a logical link is established conditional on a match, by a layer 2 procedure, of terminal identifier information before the link establishment, and thereafter call processing, by using a layer 3 message, is carried out, wherein the exchange is provided with a layer 3 control unit by which the exchange per se generates a pseudo layer 3 global reception call (broadcast type) and a layer 2 control unit which terminates the global reception call at the terminal equipment by the layer 2 procedure before the link establishment, extracts the terminal identifier information of the terminal equipment from a logical link establishment request frame which is sent from the terminal equipment in response to the termination, and notifies the terminal identifier information to the layer 3 control unit. The layer 3 control unit holds the terminal identifier information notified from the layer 2 control unit so as to use the same when later termination of a call to the terminal equipment occurs.